aot 
. Microbes, Ferments, and Moulds. 
Fuly 15, 1886 | 
NATURE 
239 
taken,” which involves solution, evaporation, &c., for 
lead sulphate, filtration, and submitting the solution to 
ordinary chemical tests. This is surely not a method 
adapted to the use of “ miners and prospectors.” 
With regard to assaying, in the case of copper ores not 
one of the ordinary methods of assay is given, and the 
ordinary method for assaying silver ores finds a place in 
an addendum to the volume. The whole book affords 
additional evidence of the prevalence of the belief in the 
fallacy that a chemist must of necessity be acquainted 
with a subject so dependent on his own, yet so widely 
differing from it, as metallurgy. 
OUR BOOK SHELF 
By E. L. Trouessart. 
“International Scientific Series.” (London: Kegan 
Paul, Trench, and Co., 1886.) 
THIS book, which aims at the instruction in microbes not 
so much of the medical and scientific as of the general 
public, is a fairly accurate exposition of the present state 
of our knowledge of the morphological and physiological 
characters of moulds and bacteria. 
Thechapters on fungiand moulds, of the various ferments 
and yeasts, and their chemistry, are the best parts of the 
book. Those on bacteria, septic and pathogenic, are 
less commendable, since they contain a good many dog- 
matic statements not accepted by bacteriologists. The 
chapter on laboratory research and culture of microbes is 
imperfect in its account of the now generally employed 
methods of cultivation on solid nutritive media. 
One of the most conspicuous deficiencies of the book in 
the eyes of the scientific reader is the one-sided account 
given by the author of many of the discoveries made in 
bacteriology, since the works of French authors form as 
it were the basis of the author’s account. It is certainly a 
novel proposition that “the science of microbes is essen- 
tially a French science.” 
The book is well illustrated, and written in a clear and 
concise manner. 
LP TTPERS, TO THE EDILOR 
[Zhe Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake to 
return, or to correspond with the writers of, rejected manu- 
scripts, No notice is taken of anonymous communications. 
[The Editor urgently requests correspondents to keep their letters 
as short as possible. The pressure on his space is so great 
that it is impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts.] 
Luminous Clouds 
THE clouds described by D. J. Rowan, on p. 192 in your 
issue of the Ist inst., seem to have been of the same kind as 
were described in several letters in NATURE last summer ; they 
were seen by myself in Bavaria. I saw these extraordinary 
clouds again this year, on the 28th of May, at Freshwater 
Bay, Isle of Wight, and on the 23rd of June at Bideford. 
They were seen by A. C. Dixon at Sunderland on the 2nd, 3rd, 
13th, 16th, 22nd, and 23rd of June, and on the latter 
date were very striking. A description of them on the same 
date, written by E. Greenhow, appeared in the Mewcastle 
Chronicle, as seen near Earsdon in Northumberland, erroneously 
describing them asa kind of aurora. On that night the display 
at Bideford was comparatively slight : at 10.18 p.m. the upper 
limit of the clouds distinctly visible was five-eighths of the way 
from the horizon to y Andromedz, and I presume that that was 
the limit to which the sun was shining upon them ; though with 
field-glasses I could see them very faintly rather higher up. 
Inever saw them before last summer, and they are quite 
different from the iridescent clouds that have created such 
interest the last two winters, resembling them only in their 
height and brilliancy. If they require a name I hope the word 
boreales, as proposed by Mr. Rowan, will not be adopted ; for 
they appear in the north only because the sun lies in that direc- 
tion, and if they occurred at any other time of the year, or in 
any place much further south than this country, their direction 
would necessarily be different. On all the occasions which I 
haye seen these clouds they have exhibited a very fine structure 
like cirrus. The colours of the clouds appear to be due to the 
same cause as the colours of the sky, for they generally corre- 
spond with these at similar altitudes, the upper visible portion 
of the sheet of clouds being green or bluish, and the lower por- 
tion a dull yellow, becoming more orange towards the horizon, 
Sunderland, July 8 T. W. BACKHOUSE 
Re Immisch’s Thermometer 
IN your article, p. 234, referring to this pretty little instru- 
ment, you refer to the appellation ‘‘ metallic” as not a happy 
one in describing it. ‘This I pointed out to the maker some 
time ago, and termed it an avityeous thermometer, as glass 
plays no part in its construction beyond that of a protector to the 
dial. The certificates of verification are printed with the instru- 
ment so designated, and probably the erroneous term will soon 
drop out of use. I must also crave permission to correct a mis- 
print in your correspondent’s statement with regard to the 
number of avitreous thermometers verified here up to the present 
date : for 500 read 300. G. M. WHIPPLE, 
Superintendent Kew Observatory 
Kew Observatory, July 1o 
Kirby and Spence’s ‘‘Introduction to Entomology ” 
WITH reference to a just complaint made by ‘* R. M.” in his 
article contained in NATURE for July 1 (p. 190) about the want 
of good indexes to books, and specially to the early editions of 
Kirby and Spence’s ‘‘ Introduction to Entomology,” may I 
venture to inform him that should an index to the latter book 
be desired by ‘‘R. M.” or any other reader of Nature, they 
have only to apply to ‘‘E. E. J.,” Camerton Court, Bath, to 
obtain one gratis. I found the book so perfectly useless for 
want of one, that I made one some years ago, a copy of which 
was accepted by the British Museum authorities, and is now 
included in their Catalogue. I have a good many copies on 
hand, which I am always glad to give away on application. 
E. E. JARRETT 
11, Holles Street, London, W., July 8 
ON VARIATIONS OF THE CLIMATE IN THE 
COURSE OF TIME? 
II. 
Le such a periodical variation in the climate does take 
place, we should be able to trace it in the older forma- 
tions, as we cannot assume that it first began to operate 
in the most recent geological age. We must, therefore, 
try to discover if such variation can be traced in the 
earlier times. 
During the melting of the Norwegian inland ice it left 
here and there moraines, and on the map drawn by 
Kjerulf they are seen to stretch in lines more or less con- 
tinuously across large parts of Southern Norway. On 
both sides of the Christiania fjord the outside lines, the so- 
called “ Raer,” stretch like gigantic ramparts from Moss 
and Horten south-east and south-west many miles wide 
through Smaalenene and far into Sweden, and, on the other 
side of the fjord, through the prevince of Jarlsberg and 
Laurvig to Jomfruland outside Krager6. And behind this 
outside line of moraines others follow in more or less 
broken but distinct continuity, one behind the other, 
through all Southern Norway. These lines show that the 
r The following is a short abstract from various papers, viz.: ‘ Essay on 
the Immigration of the Norwegian Flora during Alternating Rainy and Dry 
Periods ” (Christiania, 1876). _‘‘ Die Theorie der wechselnden kontinentalen 
und insularen Klimate,” in Engler’s Botanische ¥ahrbticher, ii. (Leipzig, 
1881). ‘* Ueber Wechsellagerung und deren mutmassliche Bedeutung fiir die 
Zeitrechnung der Geologie und fiir die Lehre yon der Verdnderung der 
Arten,” in Biologisches Centralblatt, iii. (Erlangen, 1883). ‘* Ueber die 
wahrscheinliche Ursache der periodischen Veranderungen in der Starke der 
Meeresstrémungen” é.c. iv. (Erlangen, 1384) Continued from p 222. 
